NEUTRON-SCATTERING STUDIES OF THE STRUCTURE OF A HIGHLY TETRAHEDRAL FORM OF AMORPHOUS-CARBON

The structure of amorphous carbon prepared by plasma-arc deposition has been determined by neutron scattering and analysed to estimate the fraction of tetrahedrally and trigonally bonded carbon. The mean value of the nearest neighbour C-C distance is close to that of crystalline diamond and a fit to the data for the first interatomic distance gives about 86% tetrahedral bonding. This form of diamond-like carbon therefore appears to be the structural equivalent of a-Si and a-Ge. A somewhat different interpretation is obtained from an analysis of the measured first and second peak coordination numbers and an attempt is made to reconcile the two approaches.